Appendiceal tumors

　　First, etiology

　　The obstruction of the appendiceal lumen is the key to the formation of appendiceal mucinous cysts, and the occurrence of obstruction can come from chronic inflammation of the appendiceal mucosa, scar contraction, and foreign body impaction, or from adhesion, twisting, and compression of the appendiceal wall. After the lumen is blocked, the secretions in the distal part of the appendiceal lumen cannot be normally discharged, and they gradually accumulate in the lumen, eventually leading to the expansion and dilation of the appendiceal lumen, forming a cystic structure. Only when the intraluminal pressure increases to affect the nutritional supply of the tube wall does the mucosal epithelium stop secreting mucus, and the cyst no longer increases in size. It can be seen that the occurrence and development of appendiceal mucinous cysts must meet three conditions.

　　1. The obstruction characteristics of the appendix lumen are gradually formed, mechanical, and complete.

　　2. The mucosal function of the appendix is normal after blockage, and the distal appendix mucosa can secrete mucus normally.

　　3. The internal environment of the appendix does not contain bacteria, and there is no suppurative infection.

　　Second, pathogenesis

　　The pathological types of appendiceal tumors commonly include three types:

　　1. Appendiceal carcinoid is the most common in gastrointestinal carcinoids and appendiceal tumors, accounting for about 90% of all appendiceal tumors. Carcinoid can be divided into pure carcinoid, adenoid carcinoid, and mixed carcinoid adenocarcinoma. The lesions are mostly located in the distal part of the appendix, with the tumor diameter below 1cm accounting for 70% to 90%, and above 2cm accounting for about 1%. Less than 2cm has fewer metastases, and those with metastases account for only 14% to 33%. Individual reports have shown liver metastasis and carcinoid syndrome. Under the microscope, it is common to see the tumor invading the muscular layer and lymphatic vessels. If a hard spherical mass is felt during surgery, and the cut surface is yellow or grayish yellow, it should be highly suspected. Adenoid carcinoid, which is more malignant than general carcinoid, can cause metastasis in 15% of cases.

　　2. The cyst size of appendiceal mucinous tumors ranges from a few millimeters to more than 10 centimeters, and they are divided into retention cysts, benign mucinous cystadenomas, and malignant mucinous cystadenomas, but it is difficult to distinguish between benign and malignant with the naked eye. Mucinous cystadenocarcinoma can invade cancer tissue beyond the mucosal layer of the appendix wall, can cause peritoneal implantation, and can be found in the peritoneal fluid with secretory epithelial cells.

　　3. Adenomas and adenocarcinomas are divided into villous adenomas, leiomyomas, neuromas, and others.

　　4. Others are mainly mucinous adenocarcinoma and signet ring cell carcinoma, with malignant lymphoma and leiomyosarcoma being rare.

　　1. When the tumor is large or blocks the lumen of the appendix, causing increased intraluminal pressure or compressing the mesentery of the appendix, it can lead to ischemia, congestion, and secondary infection of the appendix.

　　2. The compression of the bladder by the mass can cause frequent urination and urgency, and the compression of the ureter manifests as lumbar pain and hydronephrosis.

　　3. When the tumor volume is large or the malignant tumor infiltrates and adheres to surrounding tissues, a mass can be felt in the lower right quadrant of the abdomen. Therefore, it is necessary to repeatedly understand the history of abdominal pain during diagnosis. The abdominal pain caused by appendiceal tumors usually has a chronic process, and after treatment with anti-inflammatory drugs, there is no improvement in abdominal pain and mass. In addition, malignant tumors may have other symptoms of colorectal cancer, such as hematochezia, anemia, ascites, and distant metastasis.

　　When the tumor volume is large or the malignant tumor infiltrates and adheres to surrounding tissues, a mass can be felt in the lower right quadrant of the abdomen. Therefore, it is necessary to repeatedly understand the history of abdominal pain during diagnosis. The abdominal pain caused by appendiceal tumors usually has a chronic process, and after treatment with anti-inflammatory drugs, there is no improvement in abdominal pain and mass. In addition, malignant tumors may have other symptoms of colorectal cancer, such as hematochezia, anemia, ascites, and distant metastasis.

　　The occurrence and development of appendiceal mucinous cystadenoma must have 3 conditions:

　　1. The obstruction characteristics of the appendix lumen are gradually formed, mechanical, and complete.

　　2. The mucosal function of the appendix is normal after blockage, and the distal appendix mucosa can secrete mucus normally.

　　3. The internal environment of the appendix does not contain bacteria, and there is no suppurative infection.

　　This determines that there is no good way to prevent appendiceal tumors, and it can only be early detection, early diagnosis, and early treatment.

　　1. Ultrasound

Abdominal ultrasound is not easy to detect small appendiceal tumors, when the tumor is large, the mucinous cystadenoma presents as a circular or elliptical anechoic area or with echo of partitions, with a regular edge, clear, with mild tenderness, without history of appendectomy, malignant tumors often show uneven hyperechoic areas, with possible calcification or necrotic liquefaction areas in the middle, irregular boundaries, and in the late stage, liver metastasis foci may be found.

　　2. X-ray barium enema

　　(1) Most cases show no appendiceal shadow, and a few cases may show a shadow near the proximal end, with an interruption at the distal end. If barium enters the cyst cavity, a circular or elliptical shadow can be displayed.

　　(2) The blind-ending inner side is caused by the arc-shaped indentation due to tumor compression, and when malignant tumors involve the cecum, there may be filling defects and narrowing at the base.

　　3. Abdominal plain films can show calcification and tumor shadows.

　　1. It is advisable to eat more foods with antitumor effects, such as toads, frogs, snails, kelp, seaweed, tortoise shell, turtle, sea cucumber, water snake, Job's tears, water chestnut, walnut, goat kidney, pork kidney, dolichos, sand worm, perch, mackerel.

　　2. It is advisable to eat kelp, wakame, seaweed, and green crab.

　　3. For infection, it is advisable to eat yellowfish bladder, shark fin, water snake, pigeon, jellyfish, lotus root starch, buckwheat, horsehead grass, earth ear, turnip, olive, eggplant, fig, mung bean sprouts, soy milk, amaranth, seaweed, loach.

　　1. Treatment

　　Primary appendiceal tumors should all be surgically resected, and the surgical method varies according to the nature and location of the tumor.

　　1. The treatment for appendiceal mucinous cystadenoma is the complete resection of the appendix, which is the only treatment for benign mucinous cystadenoma. According to statistics, most cysts are located at the distal end of the appendix, and resection of the appendix including the cyst is sufficient. The operation should be gentle, and the cyst should be separated from the surrounding tissues with dressings to prevent the cyst from rupturing as much as possible. Puncture or incision exploration should be avoided to prevent the extrusion of mucus, peritoneal implantation, and the formation of pseudomyxoma peritonei. If the cyst ruptures, the mucus should be aspirated thoroughly, and the peritoneal cavity should be flushed with 500-1000mg of fluorouracil (5-FU) in 1000ml of normal saline. For malignant mucinous cystadenoma, most scholars believe that right hemicolectomy should be performed to achieve radical treatment. If the root is involved or adherent to the cecum, it is advisable to resect a part of the cecum. For those with ovarian mucinous cystadenoma or cystadenocarcinoma, the ovary should be resected simultaneously.

　　2. For appendiceal carcinoid, most scholars advocate using the size of the tumor as the main basis for choosing the surgical method. For carcinoids with a diameter greater than 2cm, the incidence of metastasis is high, and they can be considered as malignant carcinoids, and right hemicolectomy should be performed. For appendiceal carcinoids with a diameter less than 1cm, simple appendectomy is sufficient. Moertel's follow-up of 128 patients who underwent simple appendiceal carcinoid resection found that 110 patients (86%) survived for 5 years, 86 patients (67%) survived for more than 10 years, and there were no cases of metastasis or recurrence. There is much controversy regarding tumors with a diameter between 1 to 2cm, but most scholars believe that simple appendectomy can be performed, and the mesentery should be completely resected. However, for young patients, if the carcinoid diameter is greater than 1.5cm or the carcinoid has infiltrated the subserosal layer or the appendiceal mesentery, a resection of the ileocecal region or right hemicolectomy can be performed.

　　3. Most scholars believe that once the diagnosis is clear, right hemicolectomy should be performed. Compared with simple appendectomy, right hemicolectomy can significantly improve the 5-year survival rate and reduce recurrence. Since the differentiation of appendiceal adenocarcinoma is generally poor, the range of radical resection should be expanded, and right hemicolectomy should be performed once the diagnosis is clear.

　　4. Other malignant tumors are mainly mucinous adenocarcinoma and signet ring cell carcinoma, and malignant lymphoma and leiomyosarcoma are rare. Solid tumors are mostly malignant, and if the nature of the tumor cannot be determined during surgery, frozen section examination should be performed. Strive for radical resection in one stage. Due to the lack of muscular layer in the appendix, the infiltration of the mucosal sublayer indicates that the lesion has reached the serosal sublayer, and it is mostly Dukes B, C stage when found. At this time, the surgical principles for right hemicolectomy and combined treatment with chemotherapy, immunotherapy, and other comprehensive treatments should be followed for right hemicolectomy.

　　II. Prognosis

　　Surgical resection is the only effective means, with generally good prognosis, and the 5-year survival rate can reach over 90%. The literature has reported multiple cases of appendiceal adenocarcinoma with liver metastasis, where patients have survived with the tumor for more than 10 years.